The stated objective of the United Nations Framework Convention on Climate Change is to achieve “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.” The most problematic aspect of this mandate is the open definition of ‘dangerous anthropogenic interference.’ Given that we have direct ice core evidence that concentrations of carbon dioxide are higher than at any point in the past 650,000 years – along with indirect evidence that this is the peak for the last 20 million years – it is fair to say that we are already interfering dangerously with the climate system.
Of course, one cannot go straight from showing elevated CO2 to ascribing danger. That said, the link between greenhouse gasses and increases in radiative forcing and temperature is incontrovertible. So too, the realities of icecap and glacier melting and ocean acidification. The question is no longer about whether or not we will cause dangerous interference, but how much danger we are willing to tolerate in exchange for less rapid and comprehensive changes to our high-carbon lifestyles.